Process for preparing pentolite



Feb. 19, 1946. G. w. McCURDY 2,395,341

PROCESS FOR PREPARING PENTOLITE Filed Sept. 14, 1943 Gore on h/Mc Curd}! INVENTOR.

BY l -M 6AA ATTORNEY Patented Feb. 19, 1946 PROCESS FOR PREPARING PENTOLITE Gordon W. McCurdy, Radford, Va., assig-nor to Hercules Powder Company, Wilmington, Del., a corporation of Delaware Application September 14, 1943, Serial No. 502,373

Claims.

This invention relates to the art of making organic explosives and more particularly to a method for making Pentolite.

Pentolite is an organic explosive extensively used as a bursting charge in high-explosive ammunition. It consists essentially of an intimate mixture of pentaerythritol tetranitrate (PETN) and grade I trinitrotoluene (TNT). Heretofore, organic explosive mixtures of this type have been made by mechanical mixing of solid organic explosive substances or by dissolving together in a common solvent organic explosive substances and simultaneously precipitating. The latter method is the one used in the art and is set forth more specifically in U. S. Ordnance Department Tentative Specification AXS-6l2, dated July 10, 1941, section C-l, Material and workmanship. This specification in part states, Pentolite must consist of an intimate mixture of PETN and TNT grade I and must be made by dissolving the ingredients together in acetone, filtering the solution, precipitating with clean water, and drying by a suitable method Pentolite manufactured by the above process wherein the solution of the explosives in acetone is added to water contains PETN of small particle size, and, although it meets the above-designated government specifications, -it is not entirely satisfactory for melt or cast loading of the shells of high explosive ammunition due to the high viscosity of the slurry at the desired pouring temperature of 85 to 90 C. This high viscosity is attributable mainly to the presence of fine PETN in the slurry. In cast loading the Pentolite is heated in the order of 85 to 90 0., thus forming a slurry, which is poured. The temperature of 85 to 90 C. is slightly above the melting point of the TNT; consequently the slurry is a mixture of the PETN crystals with the fluid TNT, the TNT functioning as a lubricant and flow medium for the PETN during the pouring operation of filling certain types of high explosive shells. The pouring quality of the Pentolite slurry is dependent upon two factors; namely, the temperature of the mass, the higher the temperature the more fiuid the molten TNT; and the dimensions of the crystals of PETN, it being accepted in the art that fine crystals of PETN result in decreased fluidity.

On account of the inherent dangers associated type explosive with a minimum offine PETN therein so that at a temperature only slightly above the melting point of the TNT the material will be sufliciently fluid to give satisfactory casting. Too much elevation of the temperature to effect lowered viscosity and improved fiow qualities has the deleterious eifect of allowing settling out of the PETN crystals from the TNT upon standing, thus nullifying the earlier treatment to produce an intimate mixture of the two explosive ingredients.

An object of the invention is a method for the formation of an intimate mixture of organic explosive substances which is more satisfactorily cast in molds at a temperature only slightly above the melting point of the lower melting point constituent.

Another object is to devise a method of making an intimate mixture of solid organic explosive substances containing a minimum amount of fine particles of PETN.

A still further object is to devise a method of making Pentolite which is more satisfactory for casting.

Generally described, the present invention comprises a method of making an organic explosive of an intimate mixture of two organic explosive substances with differing melting points with much desired improvement in fiow properties for melt or cast loading of the shells of high explosive ammunition. Organic explosives possessing this improvement have been made by a method comprised of depositing one organic explosive from solution onto the particles of a higher melting point organic explosive substance while in the form of a slurry with a nonsolvent therefor.

More specifically, the organic explosive, possessing good pour and casting qualities in the form of a slurry made by heating the same to about C., and containing a critically smaller amount of fine particles, was prepared by a method comprised of: (1) making a slurry of particles of selected size of one organic explosive substance of melting point above C. with a liquid which is a nonsolvent therefor and is also a nonsolvent for the explosive substance to be deposited on the first substance; (2) mixing the slurry with a solution of a second organic explosive substance having a melting point slightly vbelow 85 C. in a liquid which is a solvent therefor and which is miscible with the liquid used in making the slurry in the first instance, thereby depositing the second explosive substance as a solid onto the particles of the first explosive substance; recovering the resulting conglomerate granules from the liquid mixture and drying by a suitable method. During the mixing of the solution of the second organic explosive substance with the slurry of the first organic explosive substance, the mixture was thoroughly agitated.

Having set forth the invention in a. general way it will now be described in more detail. The following is an embodiment of one method of practicing the invention: A water slurry of crystalline PETN of predetermined particle size was prepared and to this slurry was added, under agitation, TNT dissolved in acetone. Dilution of the acetone upon mixing with the water caused the TNT to precipitate and to be deposited on the PETN forming conglomerate granules which were separated from the liquid mixture and dried by antiable methods. Table I following contains representative data on the preparation of Pentolite by this slurry method. In Example A, Pentolite was prepared by making a slurry of 400 parts of. PE'I'N and 1500 parts of water at a temperature of 36 F.; 400 parts of TNT was dissolved in 600 parts of acetone and this acetone-TNT solution at a temperature in the order of 90 F. was mixed with the PETN slurry under agitation, the resulting temperature of the charge being 60 F. at the end of the mixing operation. After deposition of the TNT onto the PETN particles forming conglomerate granules of individually coated particles, the conglomerate granules were recovered from the mixture and dried by a suitable method. The sample or Pentolite obtained had a bull; density of 0.48 and a composition or" 50.3% PETN and 49.7% TNT. Examples 13 and C difiered from Example A only in slight variations of operating temperature and bulk density and composition of the resulting Pentolite, as shown in Table I.

In accordance with the present invention Pentolite was prepared with a larger percentage of crystals too large to pass a 100-mesh screen and with a smaller amount that passes a 140- mesh screen than by the former method of simultaneous precipitation of the PETN and TNT from a common solvent by addition of the solution to a precipitating liquid. Crystals having a major proportion thereof retained on a 120-mesh sieve have been found preferable. This increased percentage of large crystals with a correspondingly diminished fraction of fine crystals of PETN is responsible for the better pour qualities of explosives of PETN and TNT made by the improved process of the present invention.

The influence of particle size of the constituent PETN upon casting characteristics is clearly indicated in the accompanying drawing, forming a part of the specification wherein reference symfools refer to like parts wherever they occur:'

Fig. 1 is a fragmentary part-sectional partelevational view of a shell loaded with Pentolite having poor flow characteristics when cast at a temperature in the order of 95 0.;

Fig. 2 is a fragmentary part-sectional partelevational view of a shell loaded with the same Pentolite as that illustrated in Fig. 1, but which had improved flow characteristics due to the fact that the Pentolite wa cast at a temperaure in the order of 100 C.;

Figs. 3, 4 and 5 are fragmentary part-sectional part-elevational views of shells loaded with Pentolite prepared in accordance with the present invention having excellent flow characteristics when cast at a temperature in the order of 85 C;

Fig. 1 shows a shell l, having a conical member 3 disposed therein and held in place by a. threaded Table 1' Example A Example B Example 0 Wt. PETN 400 lbs. 400 lbs. W 1,500 lbs 1,500 lbs. (lo-18 C.) 65 F--- 60-65" F. 380 r. p. m 380 r. p. m. 400 lbs 400 lbs. 600 lbs 600 lbs.

(32 C.) 90 F 90 F.

(2 C.) 36 F 52 C.) 36 F (21 C.) F. (16 C.) 60 F 16 C.) 60 F--- (26 C.) 78 F. Pentolite:

Bulk density 0.48.-- 0.52 0.47. Composition:

PETN 50.3% 49.99 51.9%. TNT 49.7% 50.1 a 48.1%.

Table II Screen test Example A Example B Example 0 Regular Percent Percent Percent Percent On 80 mesh 50. 9 70. 8 45. 9. 9 On 100 mesh 12. 6 l0. 9 12.9 3.0 4. 7 4. 6 6. 3 l. 8 10. 2 6. 5 l0. 3 35. 1 7. 8 3. 2 7. l 36. 6 13. 8 4. 0 l7. 8 13. 6

Fig. 1.

plug (not shown), which threadedly engages the threads 5 of the shell casing l. The shell casing I was filled with Pentolite '7. The Pentolite Z was prepared in accordance with prior art methods and exhibited poor flow characteristics as indicated by the annular cavity 3. The annulus 9 rendered the shell particularly susceptible to set back even after the threaded plug (not.

shown) was tightly secured in place. The Pentolite was cast at a temperature in the order of C.

In Fig. 2 a shell I' having the same construction I as that shown in Fig. 1 was filled with Pentolite 7 prepared in accordance with prior art methods, but was cast at a temperature in the order of C. which gave improved flow characteristics and eliminated the annular cavity illustrated in In Figs. 3, 4 and 5, shells I having the same construction as those shown in Figs. 1 and 2 were filled with Pentolite 11 prepared in accordance with the method of the present invention. These shells were filled with the Pentolite compositions of Examples A, B and C of Table 1, respectively, and had excellent flow characteristics when cast at a low temperature in the order of 85 C.

The foregoing examples are by way of illustration and the invention is not limited to a 50/50 composition of PETN and TNT, but any desired combinations may be used. Furthermore, the particle size of the PETN may be varied to suit conditions.

From the foregoing it will be seen that the present invention provides a method of making an organic explosive comprised of two organic explosive substances of differing melting points, such that by heating the intimate mixture to a temperature only slightly above the melting point of 'the lower melting point constituent,"a slurry will be obtained which possesses flow characteristics dependent upon the predetermined particle size of the higher melting point organic explosive substance. The particle size of the PETN may be determined independently of any conditions imposed by virtue of the presence of TNT or any other organic explosive in using the method of simultaneous precipitation of both explosive substances from a common solvent. Consequently, the pour quality of the explosive mixture at a given temperature for a given combination may be predetermined by independently determining the crystal size of the higher melting point explosive ingredient. Application of this method to making an explosive mixture of PETN and TNT with particles of PETN of predetermined size so as to contain crystals having a major proportion thereof retained on a 120-rnesh sieve with only a small proportion of crystals passing through a ZOO-mesh screen gives an explosive with excellent pour characteristics for casting in high-explosive ammunition.

This method has the advantage over prior methods of definite control of the particle size of the higher melting point substance in the resultant organic explosive mixture, less acetone required, and faster drying of the conglomerate mass.

What I claim and desire to protect by Letters Patent is:

1. A process for preparing Pentolite which has improved flow properties for casting operations which comprises making a slurry of 400 parts of PETN and 1500 parts of water, said PETN having a major proportion thereof retained on a. 120-mesh sieve; making a solution of 400 parts of TNT and 600 parts of acetone; adding said solution to said slurry while continuously agitating to precipitate the TNT upon dilution of the acetone with the water, whereby the said TNT is deposited on the PETN forming conglomerate granules of individually coated particles; withdrawing said conglomerate granules and drying.

2. A process for preparing Pentolite which has improved flow properties for casting operations which comprises making a slurry of PETN and water, said PETN having a major proportion thereof retained on a 120-mesh sieve; making a solution of TNT and acetone; adding said solution to said slurry in the presence of excess water while continuously agitating to precipitate the TNT upon dilution of the acetone with the water, whereby the said TNT is deposited on the PETN forming conglomerate granules of individually coated particles; withdrawing said conglomerate granules and drying.

3. A process for preparing Pentolite which has improved flow properties for casting operations which comprises making a water slurry of crystalline PETN, said PETN being of such particle size that a major proportion thereof is retained on a '120-mesh sieve; agitating said slurry and adding particle size; agitating said slurry and adding TNT dissolved in acetone, whereby the dilution of the acetone by the water of the slurry causes the TNT to precipitate and be deposited on the PETN forming conglomerate granules of individually coated particles; withdrawing said conglomerate granules and drying.

5. A process for preparing an organic explosive which has improved flow properties for casting operations which comprises making a slurry of a crystalline organic explosive with a liquid which is a nonsolvent therefor, said crystalline organic explosive being of predetermined particle size; agitating said slurry and adding a lower melting point organic explosive dissolved in a solvent which is miscible with said liquid, the said liquid being a nonsolvent for said lower melting point organic explosive, whereby the dilution of the solvent by the liquid of the slurry causes the lower melting point organic explosive to precipitate and be deposited on the particles of the crystalline organic explosive forming conglomerate granules of individually coated particles; withdrawing said conglomerate granules and drying.

6. A process for preparing an organic explosive which has improved flow properties for casting operations which comprises making a slurry of a crystalline organic explosive having a melting point above about C. with a liquid which is a nonsolvent therefor, said crystalline organic explosive being of predetermined particle size; agitating said slurry and adding TNT dissolved in a solvent which is miscible with said liquid the said liquid being a nonsolvent for TNT, whereby the dilution of the solvent by the liquid of the slurry causes the TNT to precipitate and be deposited on the particles of the crystalline organic explosive forming conglomerate granules of individually coated particles; withdrawing said conglomerate granules and drying.

7. In the method of casting Pentolite in shells for high-explosive ammunition, the steps which comprise making a slurry of 400 parts of PETN and 1500 parts of water, said PETN having a major proportion thereof retained on a. 120-mesh sieve; making a solution of 400 parts of TNT and 600 parts of acetone; adding said solution to said slurry while continuously agitating to precipitate the TNT upon dilution of the acetone with the water, whereby the said TNT i deposited on the PETN forming conglomerate granules of individually coated particles; withdrawing said conglomerate granules and drying; heating the dried granules to a temperature from about 85to about C. and pouring said heated granules into shells.

8. In the method of casting Pentolite in shells for high-explosive ammunition, the steps which comprise making a slurry of PETN and water. said PETN having a major proportion thereof retained on a lifi-mesh sieve; making a solution of TNT and acetone; adding said solution to said slurry in the presence of excess water while continuously agitating to precipitate the TNT upon dilution of the acetone with the water, whereby for high-explosive ammunition, the steps which comprise making a water slurry of crystalline PE'I'N, said PEI'N being of such particle size that .a major proportion thereof is retained on a 120- mesh sieve; agitating said slurry and adding TNT dissolved in acetone, whereby the dilution of the acetone by the water of the slurry causes the TNT to precipitate and be deposited on the PETN forming congiomerate grannies of'individnaiiy coated particles; withdrawing said ccnglcmerate granules and drying; heating the dried granules to a temperature from about 85 to about 95 C. and pouring the heated mass into shells.

10. In the methodoi casting Pentolite in molds for high-explosive ammunition, the steps which comprise making a. water slurry of crystalline PETN, said PE'IN being of predetermined particle size; agitating said slurry and adding TNT dissolved in acetone, whereby the dilution of the acetone by the water of the slurry causes the TNT to precipitate and be deposited on the PETN forming conglomerate granules of individually coated particles; withdrawing said conglomerate granules and dryingyheating the dried granules to a temperature from about to about C. and pouring the heated mass into molds. 

